Vasopressin function in hypercalcaemia

Vasopressin function and thirst were studied in fourteen hypercalcaemic patients (ten hyperparathyroid and four disseminated malignant disease). Ten patients had decreased renal concentrating ability which reversed within a few days in the majority of patients whose hypercalcaemia was corrected by parathyroidectomy. Although eight patients complained of thirst, none showed a lowered threshold of thirst appreciation during hypertonic saline infusion. Osmoregulation of vasopressin secretion was not reduced in any patient, but the hyperparathyroid group had an exaggerated vasopressin response to osmotic stimulation. We conclude that a partial, reversible nephrogenic diabetes insipidus occurs in at least 70% of hypercalcaemic patients irrespective of cause, which accounts for the polyuria induced by hypercalcaemia.